JPH11160512A - Diffraction optical element and optical system using the same - Google Patents
Diffraction optical element and optical system using the sameInfo
- Publication number
- JPH11160512A JPH11160512A JP34218697A JP34218697A JPH11160512A JP H11160512 A JPH11160512 A JP H11160512A JP 34218697 A JP34218697 A JP 34218697A JP 34218697 A JP34218697 A JP 34218697A JP H11160512 A JPH11160512 A JP H11160512A
- Authority
- JP
- Japan
- Prior art keywords
- grating
- optical element
- diffractive optical
- diffraction
- different
- Prior art date
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Abstract
Description
【0001】[0001]
【発明の属する技術分野】本発明は回折光学素子及びそ
れを用いた光学系に関し、特に使用波長領域の光束が特
定次数(設計次数)に集中するような回折格子構造を有
し、所望の分光特性が高い回折効率で得られる写真用カ
メラ、ビデオカメラ、双眼鏡、プロジェクター、望遠
鏡、顕微鏡、複写機等の各種の光学系に好適なものであ
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffractive optical element and an optical system using the same, and more particularly to a diffractive optical element having a diffraction grating structure in which a light beam in a used wavelength region is concentrated on a specific order (design order). It is suitable for various optical systems such as a photographic camera, a video camera, binoculars, a projector, a telescope, a microscope, and a copying machine, which can obtain characteristics with high diffraction efficiency.
【0002】[0002]
【従来の技術】従来より回折光学素子が種々と提案され
ている。例えば特公平7-92526号公報には基板上の中央
部に断面形状が鋸歯形状のグレーティング部と周辺部に
断面形状が矩形状のグレーティング部とを設けたグレー
ティングレンズを開示している。2. Description of the Related Art Conventionally, various diffractive optical elements have been proposed. For example, Japanese Patent Publication No. 7-92526 discloses a grating lens in which a grating portion having a sawtooth cross-sectional shape is provided at a central portion on a substrate and a grating portion having a rectangular cross-sectional shape is provided at a peripheral portion.
【0003】又、特開平7-113906号公報には階段形状の
ステップ数が異なり、又、最大膜厚がステップ数によっ
て異なるグレーティング部を具備する回折光学素子を開
示している。Japanese Patent Application Laid-Open No. Hei 7-113906 discloses a diffractive optical element having a grating portion in which the number of steps in a staircase shape differs and the maximum film thickness varies depending on the number of steps.
【0004】一方、光学系には種々の諸収差が存在し、
これらの収差を補正するように各光学要素が組み立てら
れている。従来より光学系に於いて発生する諸収差のう
ち色収差は、分散特性の異なる硝材を組み合わせること
により減じていた。例えば、望遠鏡等の対物レンズで
は、分散の小さい硝材を正レンズとし分散の大きい硝材
を負レンズとし、これらを組み合わせることで軸上に現
れる色収差を消していた。このためレンズの構成枚数が
制限される場合や使用できる硝材が限られている場合な
どでは色収差の補正を十分にすることができなかった。On the other hand, the optical system has various aberrations,
Each optical element is assembled so as to correct these aberrations. Conventionally, chromatic aberration among various aberrations generated in an optical system has been reduced by combining glass materials having different dispersion characteristics. For example, in an objective lens such as a telescope, a glass material having a small dispersion is used as a positive lens, and a glass material having a large dispersion is used as a negative lens. For this reason, when the number of constituent lenses is limited, or when the usable glass material is limited, the chromatic aberration cannot be sufficiently corrected.
【0005】また、従来の硝材の組み合わせにより色収
差を減じる方法に対して、レンズ面やあるいは光学系の
1部に回折作用を有する回折光学素子(以下「回折格
子」とも言う)を設けることで、色収差を減じる方法が
SPIE Vol.1354 InternationalLens Design Conference
(1990)等の文献や特開平4-213421号公報、特開平6-3242
62号公報、USP5,044,706 等により開示されている。
これは、光学系中の屈折面と回折面とでは、ある基準波
長の光線に対する色収差の出方が逆方向に発現するとい
う物理現象を利用したものである。In contrast to the conventional method of reducing chromatic aberration by combining glass materials, a diffractive optical element (hereinafter also referred to as a “diffraction grating”) having a diffractive action is provided on a lens surface or a part of an optical system. How to reduce chromatic aberration
SPIE Vol.1354 InternationalLens Design Conference
(1990) etc. and JP-A-4-213421, JP-A-6-3242
No. 62, US Pat. No. 5,044,706 and the like.
This utilizes a physical phenomenon in which chromatic aberration appears with respect to a light beam having a certain reference wavelength in the opposite direction between the refraction surface and the diffraction surface in the optical system.
【0006】ここで、回折効果を利用した光学系では、
使用波長領域の光束が特定次数(以後設計次数という)
に集中するように格子構造を決定している。特定の次数
に光の強度が集中している場合では、それ以外の回折光
の光線の強度は低いものとなり、強度が0の場合にはそ
の回折光は存在しないものとなる。しかし、使用波長領
域が可視光領域のように広波長域の場合は、全ての波長
の光で設計次数のみの回折光とすることは格子構造上容
易ではない。そして設計次数以外の回折次数をもった光
線は、設計次数の光線とは別な所に結像するため、フレ
アとなり、像のコントラストの低下を引き起こす。この
悪影響を防止する手段として特開平8-220482号公報で
は、回折光学素子を複数の領域エリアに分割し、各エリ
アで最適となる回折効率が異なるように格子厚を変え、
各エリアにそのエリアで回折効率が最大となる波長付近
の帯域光が照射されるように波長選択する光学系が提案
されている。Here, in an optical system utilizing the diffraction effect,
The luminous flux in the used wavelength region is a specific order (hereinafter called the design order)
The lattice structure is determined so as to concentrate on. When the light intensity is concentrated to a specific order, the intensity of the other diffracted light beams is low, and when the intensity is 0, the diffracted light does not exist. However, when the wavelength region to be used is a wide wavelength region such as a visible light region, it is not easy due to the lattice structure to make the light of all wavelengths into the diffracted light of only the design order. Light rays having a diffraction order other than the design order form an image at a place different from the light rays of the design order, so that a flare occurs and the image contrast is reduced. As means for preventing this adverse effect, in JP-A-8-220482, the diffractive optical element is divided into a plurality of area areas, and the grating thickness is changed so that the optimum diffraction efficiency differs in each area.
An optical system has been proposed that selects a wavelength so that each area is irradiated with a band of light near a wavelength at which the diffraction efficiency is maximum in that area.
【0007】一方、回折光学素子として階段状の格子を
多段重ね合わせた構造のものが種々と提案されている。On the other hand, various types of diffractive optical elements having a structure in which step-like gratings are stacked in multiple stages have been proposed.
【0008】この多段型の回折光学素子を製造する方法
として例えばUSP4,895,790 ではn個のマスクで2n
段の多段型の回折光学素子をエッチングプロセスにより
製造する方法が提案されている。尚、以下述べるエッチ
ングプロセスは、フォトリソグラフィプロセスの内、基
板へのフォトレジストコーティング、マスクアライメン
ト、露光、現像、エッチング、レジスト除去の一連の処
理のことを言う。[0008] 2 n In this multi-stage n-number of mask in example USP4,895,790 as a method for producing a diffractive optical element
A method for manufacturing a multi-stage diffractive optical element by an etching process has been proposed. Note that the etching process described below refers to a series of processes of a photoresist coating on a substrate, mask alignment, exposure, development, etching, and resist removal in a photolithography process.
【0009】[0009]
【発明が解決しようとする課題】回折光学素子として光
入射面を複数の領域に分割し、各領域で異なった格子厚
で回折格子を構成した複数の格子厚を有する多段型の回
折光学素子を前記フォトリソグラフィプロセスを利用し
て、製造するためにはかなりの製造工程が生じてしま
う。ここで、図6に示すような異なる格子厚d1、d2
を有する多段型の回折光学素子を製造する場合について
述べる。ここで各格子部2、3は8段の階段構造からな
り、2種類の異なる格子厚を有するものとする。このよ
うな回折光学素子を型による成形で製作する場合の、型
の製造手順を図7に示す。As a diffractive optical element, a multi-stage diffractive optical element having a plurality of grating thicknesses in which a light incident surface is divided into a plurality of regions and a diffraction grating is formed with a different grating thickness in each region. To manufacture using the photolithography process, considerable manufacturing steps are required. Here, different grating thicknesses d1 and d2 as shown in FIG.
A case of manufacturing a multi-stage diffractive optical element having the following will be described. Here, each of the lattice portions 2 and 3 has an eight-step structure, and has two different lattice thicknesses. FIG. 7 shows a mold manufacturing procedure when such a diffractive optical element is manufactured by molding with a mold.
【0010】まず、第1マスクによって格子部2を遮光
し格子部3に対しUSP4,895,790に記述されているよ
うな製造手段を適応する。従って8段の回折格子では、
第2、第3マスクを用いた3回のエッチング処理が行わ
れる。次に第4マスクによって格子部3を遮光し、格子
部2に対して同様な処理が行われる。つまり、1種類の
格子厚を製造する際には他の格子厚の部分は遮断し、各
格子厚毎に順々にこの過程を繰り返すことで異なる格子
厚を有する回折光学素子を製造することになる。そのた
め各異なる格子厚を有する格子部に対応する分だけマス
クの種類が増えることになる。2n の格子段数より成る
m種類の異なる格子厚を有する回折光学素子を製造する
場合にはm×n種類のマスクが必要となる。First, the grating portion 2 is shielded from light by the first mask, and a manufacturing means as described in US Pat. No. 4,895,790 is applied to the grating portion 3. Therefore, in an 8-stage diffraction grating,
Etching is performed three times using the second and third masks. Next, the grid portion 3 is shielded from light by the fourth mask, and the same process is performed on the grid portion 2. In other words, when manufacturing one kind of grating thickness, the other grating thickness portions are cut off, and this process is repeated for each grating thickness in order to manufacture a diffractive optical element having a different grating thickness. Become. Therefore, the number of types of masks is increased by an amount corresponding to the grating portions having different grating thicknesses. When manufacturing diffractive optical elements having m kinds of different grating thicknesses with 2 n grating steps, m × n kinds of masks are required.
【0011】前述の例では2×3=6種類のマスクが必
要になる。また、これに伴いエッチングプロセスも増
え、製造時間も通常のm倍の時間が必要になり、生産性
は低下する。さらにこの場合、各格子厚を製造する際の
エッチングを行う深さが各々で異なり、厚みの制御が困
難になっている。In the above example, 2 × 3 = 6 types of masks are required. In addition, the number of etching processes is increased, and the manufacturing time is required to be m times longer than usual, thus lowering the productivity. Further, in this case, the etching depth for manufacturing each lattice thickness is different from each other, and it is difficult to control the thickness.
【0012】本発明は簡単な工程で特にエッチングマス
クの数を削減することによる、製造時間の大幅な削減を
図りつつ容易に製造することができる回折光学素子の製
造方法及びそれを用いた回折光学素子の提供を目的とす
る。The present invention relates to a method for manufacturing a diffractive optical element which can be easily manufactured while reducing the number of etching masks in a simple process, while greatly reducing the manufacturing time, and a diffractive optical element using the same. The purpose is to provide an element.
【0013】[0013]
【課題を解決するための手段】本発明の回折光学素子は (1−1)基板上を複数の領域に分割し、各領域ごとに
格子段数及び格子厚が異なるレンズ作用を有する断面形
状が階段形状より成る回折格子を設けて複数の格子部を
形成しており、該複数の格子部は回折効率の高くなる波
長が互いに異なっていることを特徴としている。The diffractive optical element according to the present invention comprises: (1-1) a substrate is divided into a plurality of regions, and the number of lattice steps and the lattice thickness of each region are different from each other. A plurality of grating portions are formed by providing a diffraction grating having a shape, and the plurality of grating portions are characterized by different wavelengths at which diffraction efficiency is increased.
【0014】特に (1−1−1)所定波長の光が前記複数の格子部で回折
されるとき、該格子部は特定次数に光束が集光している
こと。In particular, (1-1-1) that when light of a predetermined wavelength is diffracted by the plurality of grating portions, the grating portions converge a light beam to a specific order.
【0015】(1−1−2)前記回折光学素子の設計波
長は、格子段数の大きい格子部が、設計波長が長波長で
あること。(1-1-2) The design wavelength of the diffractive optical element is such that the grating portion having a large number of grating steps has a long design wavelength.
【0016】(1−1−3)前記回折光学素子の異なる
格子段数の格子部内、最も少ない格子段数からなる格子
部の各格子厚形状と、他の格子部の前記最小段数までの
各格子厚形状が等しいこと。(1-1-3) Each grating thickness shape of the grating portion having the smallest number of grating stages in the grating portions having different grating stages of the diffractive optical element, and each grating thickness of the other grating portions up to the minimum stage number. Equal shape.
【0017】(1−1−4)前記回折光学素子の複数の
格子部はラジアル方向に同心円状に分割しており、円中
心から離れるに従った格子部の方が格子厚が減少してい
ること等を特徴としている。(1-1-4) The plurality of grating portions of the diffractive optical element are divided concentrically in the radial direction, and the grating thickness decreases as the distance from the center of the circle increases. It is characterized by
【0018】本発明の回折光学素子の製造方法は (2−1)構成(1−1)の回折光学素子をその格子部
の異なる格子段数の内、最も大きい格子段数(最大段
数)をm1、nを整数としたとき 2n <m1≦2n+1 を満足する(n+1)個のマスクを用いて製造している
ことを特徴としている。The method of manufacturing a diffractive optical element according to the present invention is as follows: (2-1) The diffractive optical element having the configuration (1-1) has the largest number of grating steps (maximum number of steps) m1, It is characterized in that it is manufactured using (n + 1) masks satisfying 2 n <m1 ≦ 2 n + 1 where n is an integer.
【0019】本発明の光学系は (3−1)構成(1−1)の回折光学素子を用いている
ことを特徴としている。The optical system of the present invention is characterized in that (3-1) a diffractive optical element having the configuration (1-1) is used.
【0020】(3−2)構成(2−1)の回折光学素子
の製造方法で製造した回折光学素子を用いていること特
徴としている。(3-2) It is characterized in that a diffractive optical element manufactured by the method for manufacturing a diffractive optical element having the configuration (2-1) is used.
【0021】[0021]
【発明の実施の形態】図1は本発明の回折光学素子の要
部正面図である。図中1は回折光学素子であり、基板上
を複数の領域に分割し、該複数の領域に各領域毎に格子
段数及び格子厚が異なるレンズ作用を有する回折格子を
設けた格子部を有している。FIG. 1 is a front view of a principal part of a diffractive optical element according to the present invention. In the drawing, reference numeral 1 denotes a diffractive optical element, which has a grating portion in which a substrate is divided into a plurality of regions, and the plurality of regions are provided with a diffraction grating having a lens function in which the number of grating stages and the grating thickness are different for each region. ing.
【0022】同図では、第1、第2、第3、格子部2、
3、4の3つの領域について説明しているが3つ以上あ
っても良い。In FIG. 1, first, second, third, grid portions 2,
Although the three regions 3 and 4 have been described, three or more regions may be provided.
【0023】図2は図1の第1格子部2と第2格子部3
との境界部の断面説明図である。第1格子部2と第2格
子部3の格子厚はd1、d2である。格子断面形状は階
段形状(バイナリー形状)の格子より成っている。FIG. 2 shows the first grid portion 2 and the second grid portion 3 of FIG.
FIG. 4 is an explanatory cross-sectional view of a boundary portion between the two. The grating thicknesses of the first grating portion 2 and the second grating portion 3 are d1 and d2. The lattice cross-sectional shape is composed of a step-like (binary) lattice.
【0024】第1格子部2は9段の階段格子、第2格子
部3は8段の階段格子から構成されている。ここで、第
1格子部2の9段の各格子の格子厚を見てみると、一番
厚い箇所(図中格子a1)以外の各格子の格子厚は9段
の第1格子部2と8段の第2格子部3で同じ厚みにな
る。つまり、図中格子b1と格子a2、格子i1と格子
h2が同じ格子厚を有している。第3格子部4の格子段
数は第1、第2格子部2、3の格子段数と異なってい
る。The first grating section 2 is composed of a 9-step stair lattice, and the second lattice section 3 is composed of an 8-step stair lattice. Here, looking at the grid thicknesses of the nine grids of the first grid portion 2, the grid thicknesses of the grids other than the thickest portion (the grid a 1 in the figure) are the same as those of the nine grids of the first grid portion 2. The same thickness is obtained in the eight stages of the second grid portions 3. That is, in the drawing, the grating b1 and the grating a2, and the grating i1 and the grating h2 have the same grating thickness. The number of lattice steps of the third lattice part 4 is different from the number of lattice steps of the first and second lattice parts 2 and 3.
【0025】本実施形態の回折光学素子は使用波長領域
の光束が特定次数(設計次数)に集中する多段形状の格
子構造より成っている。各格子部では最も回折効率の高
くなる波長(設計波長)が異なっている。The diffractive optical element according to the present embodiment has a multi-stage grating structure in which the luminous flux in the used wavelength region is concentrated on a specific order (design order). The wavelength at which the diffraction efficiency is highest (design wavelength) is different in each grating portion.
【0026】例えば、格子段数の多い格子部の方が格子
段数の少ない格子部に比べて最も回折効率の高くなる波
長が長くなっている。For example, the wavelength at which the diffraction efficiency is highest is longer in a grating portion having a larger number of grating stages than in a grating portion having a smaller number of grating stages.
【0027】図1の実施形態では同心円状に複数の領域
に分割し、円中心から離れるに従って格子部の格子厚が
減少するようにしている。In the embodiment shown in FIG. 1, the area is divided concentrically into a plurality of regions, and the lattice thickness of the lattice part decreases as the distance from the center of the circle increases.
【0028】さらに、回折光学素子の異なる格子段数の
内、最も少ない格子段数(最小段数)から成る格子部の
各格子厚形状と、他の格子段数の前記最小段数までの各
格子厚形状が等しくなっている。Further, among the different grating stages of the diffractive optical element, each grating thickness shape of the grating portion having the smallest number of grating stages (minimum number of stages) is equal to each grating thickness shape up to the minimum number of other grating stages. Has become.
【0029】次に本実施形態の回折光学素子を、プラス
チックモールド等の型成形で制作する場合の型の製造手
順を図3に示す。図3においてまず1回目のエッチング
プロセスで第1マスクを用いて第1格子部2の各格子a
1、b1、c1、d1、e1、第2格子部3の格子a
2、b2、c2、d2を削ることで、2段の階段格子を
製造する。次に2回目のエッチングプロセスで第2マス
クを用いて第1格子部2の各格子a1、b1、c1、f
1、g1、第2格子部3の各格子a2、b2、e2、f
2を1回目のエッチングの半分の深さに削り取る。3回
目のエッチングプロセスで第3マスクを用いて第1格子
部2の各格子a1、b1、d1、f1、h1、第2格子
部3の各格子a2、c2、e2、g2をさらに半分、1
回目のエッチングに対して1/4の深さに削り取る。以
上の処理により第1、第2格子部2、3ともに8段の階
段形状の格子が作成されている。第2格子部3に関して
は、8段の格子形状であるので、製造プロセスは終了す
る。そして最後に4回目のエッチングプロセスで第4マ
スクを用いて第2格子部3は遮光し、第1格子部2の格
子a1のみ3回目と同じ深さに削り取ることで第1格子
部2は9段の階段形状の回折格子部が作成される。上述
の構成は各格子の格子厚が全て等しい場合の製造方法に
ついて説明した。この場合、エッチングプロセスでのエ
ッチング深さは3種類と、従来例の6種類の異なる深さ
に対し大幅に削減され、それにより深さ方向の制御は大
幅に簡素化されている。また、エッチングプロセスも従
来例では6回必要だったのに比べ4回と削減され、製造
工程も大幅に短縮されている。Next, FIG. 3 shows a mold manufacturing procedure in the case where the diffractive optical element of this embodiment is manufactured by molding such as a plastic mold. In FIG. 3, first, in the first etching process, each lattice a of the first lattice part 2 is formed using the first mask.
1, b1, c1, d1, e1, the lattice a of the second lattice part 3
By cutting 2, b2, c2 and d2, a two-step staircase lattice is manufactured. Next, in the second etching process, each of the grids a1, b1, c1, and f of the first grid portion 2 is formed using the second mask.
1, g1, each lattice a2, b2, e2, f of the second lattice part 3
2 is cut off to half the depth of the first etching. In the third etching process, each of the lattices a1, b1, d1, f1, and h1 of the first lattice unit 2 and each of the lattices a2, c2, e2, and g2 of the second lattice unit 3 are further reduced by half by using a third mask.
It is shaved to a quarter of the depth of the second etching. Through the above processing, an eight-step staircase-like lattice is created in each of the first and second lattice units 2 and 3. Since the second grid portion 3 has an eight-stage grid shape, the manufacturing process ends. Finally, in the fourth etching process, the second grating portion 3 is shielded from light by using a fourth mask, and only the grating a1 of the first grating portion 2 is shaved to the same depth as that of the third grating portion. A step-shaped diffraction grating portion is created. The above-described configuration has described the manufacturing method in the case where the grating thicknesses of all the gratings are all equal. In this case, the etching depth in the etching process is greatly reduced from the three different depths of the conventional example to three types, whereby the control in the depth direction is greatly simplified. In addition, the number of etching processes is reduced to four compared to six in the conventional example, and the manufacturing process is greatly reduced.
【0030】尚、第1、第2格子部2、3と格子段数の
異なる第3格子部4の各格子の製造手順も第1、第2格
子部2、3を製造するのと同様である。The procedure for manufacturing each of the first and second grating portions 2 and 3 and the third grating portion 4 having a different number of grating steps is the same as that for manufacturing the first and second grating portions 2 and 3. .
【0031】次に本発明の実施形態2について述べる。Next, a second embodiment of the present invention will be described.
【0032】前記実施形態1は異なる格子段数が2種類
の場合についての製造方法について述べた。また、異な
る格子段数が2n 段の格子段数からなる回折光学素子に
ついては、例えばUSP4,895,790 に示されている製法
で作れば良い。本実施形態では、それ以外の格子段数を
有する回折光学素子を作成する際の最も少ないエッチン
グプロセスで作成している。The first embodiment has described the manufacturing method in the case where the number of different grating stages is two. A diffractive optical element having a different number of grating steps of 2 n may be manufactured by the manufacturing method shown in, for example, US Pat. No. 4,895,790. In this embodiment, the diffractive optical element having the other number of grating steps is formed by the least etching process.
【0033】次に本実施形態の特徴として図4に例とし
て9段から16段までの格子段数の回折格子の製造方法
を示した。この場合も前述の実施例と同じく型を製作す
る手順について述べる。ここで、ハッチング等のパター
ンが描かれている箇所が、図3において、各エッチング
プロセスにより削り取られる箇所を表している。従って
エッチング用のマスク形状としては、9段の例をとる
と、第1回目のエッチング用マスクは、図中、第1マス
クエッチングのみ露光され、それ以外は遮光されるよう
なマスク形状を用いる。図4の各階段の製造手順からわ
かるように、16段までの階段格子なら、エッチングプ
ロセスは4回で実現できる。Next, as a feature of this embodiment, FIG. 4 shows an example of a method of manufacturing a diffraction grating having 9 to 16 steps. In this case as well, the procedure for manufacturing the mold will be described in the same manner as in the above embodiment. Here, the portion where the pattern such as hatching is drawn indicates the portion that is cut off by each etching process in FIG. Therefore, assuming that the mask shape for the etching has nine steps, the first etching mask has a mask shape in which only the first mask etching is exposed in the drawing and the other portions are shielded from light. As can be seen from the manufacturing procedure of each step in FIG. 4, the etching process can be realized in four times with a stepped lattice of up to 16 steps.
【0034】従来の製法で9種類の異なる格子厚を実現
しようとした場合、8段の格子形状だと、9×3=27
回ものエッチングプロセスが繰り返されていた。このよ
うにマスク形状を適切に設定することで、2種類以上の
複数の異なる格子厚(格子段数)が必要な場合も、大幅
に製造工程を短縮及び簡素化することが可能になる。When nine different lattice thicknesses are to be realized by the conventional manufacturing method, if the lattice shape has eight stages, 9 × 3 = 27.
The etching process was repeated many times. By appropriately setting the mask shape in this manner, even when two or more different grating thicknesses (number of grating stages) are required, the manufacturing process can be significantly shortened and simplified.
【0035】さらに、この製造手段の特徴をまとめる
と、n個のマスクによるエッチング処理で、最大格子段
数が2n 以下の格子段数については、任意の格子段数を
製造することが可能となる。そしてn個のマスクからは
最大2n −1種類の異なる格子厚(格子段数)をもつ回
折光学素子を製造することができる。Further, the characteristics of this manufacturing means can be summarized as follows. With an etching process using n masks, it is possible to manufacture an arbitrary number of lattice steps with a maximum lattice number of 2 n or less. Then, from the n masks, diffractive optical elements having a maximum of 2 n -1 types of different grating thicknesses (number of grating stages) can be manufactured.
【0036】次に本発明の実施形態3について説明す
る。Next, a third embodiment of the present invention will be described.
【0037】図5は、特開平8-220482号公報にも示され
ているようなRGB3色に対応した色光毎に回折光学素
子の回折格子厚を最適形状とした際の各格子部の設計次
数での回折効率を表したものである。各領域で高い回折
効率を維持していることが判る。ここで、異なる格子厚
の回折格子部の配置は、図1に示したような同心円状の
エリアに分割してもよいし、桝目状のエリアに分割して
もよい。FIG. 5 shows the design order of each grating portion when the diffraction grating thickness of the diffractive optical element is set to the optimum shape for each of the three colors of RGB corresponding to the colors as disclosed in Japanese Patent Application Laid-Open No. 8-220482. 2 shows the diffraction efficiency at. It can be seen that high diffraction efficiency is maintained in each region. Here, the arrangement of the diffraction grating portions having different grating thicknesses may be divided into concentric areas as shown in FIG. 1 or divided into grid-shaped areas.
【0038】次に本実施形態での格子形状について、具
体的な形状をもとに説明する。3種類の格子段数からな
る格子厚がRGBの各波長帯域で回折効率が最大となる
ような組み合わせを選択する。この場合、格子段数とし
て、青帯域に11段、緑帯域に13段、赤帯域に15段
の格子段数を割り当てる。そして、青帯域で回折効率が
最大となる波長(以下設計波長という)を450nmに
最適化すると、本発明の実施形態では、緑帯域の設計波
長は532nm、赤帯域の設計波長は614nmとな
る。ここで各領域のBGRの1段の格子深さdB、d
G、dRは基板の屈折率を1.52とすると d=λ/(n−1)m λ:設計波長 n:屈折率
m:格子段数 より dB=dG=78.7nm となる。このように異なる色光に対応して格子段数を異
ならせることにより各波長帯域毎に、最適となる設計波
長を設定することができる。また、各格子厚間で1段当
たりの格子深さは同じであるので、エッチングプロセス
も同時に行うことが可能である。Next, the lattice shape in this embodiment will be described based on a specific shape. A combination is selected such that the grating thickness of the three types of grating stages maximizes the diffraction efficiency in each of the RGB wavelength bands. In this case, as the number of grid steps, 11 steps are allocated to the blue band, 13 steps to the green band, and 15 steps to the red band. When the wavelength at which the diffraction efficiency is maximized in the blue band (hereinafter, referred to as the design wavelength) is optimized to 450 nm, in the embodiment of the present invention, the design wavelength in the green band is 532 nm, and the design wavelength in the red band is 614 nm. Here, one-stage lattice depth dB, d of BGR of each region
G and dR are assuming that the refractive index of the substrate is 1.52. D = λ / (n−1) m λ: Design wavelength n: Refractive index
m: dB = dG = 78.7 nm from the number of grating stages. By making the number of grating stages different in accordance with different color light in this way, an optimal design wavelength can be set for each wavelength band. Further, since the grating depth per stage is the same between the respective grating thicknesses, the etching process can be performed simultaneously.
【0039】本実施形態では、可視光領域において使用
される回折光学素子について示したが、この波長領域に
限定するものでなく、使用する波長領域がある程度広帯
域な系であれば、その波長領域が赤外光の領域であって
も可視光から赤外光にわたる場合であっても同様の効果
が得られる。In this embodiment, the diffractive optical element used in the visible light region has been described. However, the present invention is not limited to this wavelength region. The same effect can be obtained even in the range of infrared light or in the range from visible light to infrared light.
【0040】また、各実施形態の説明では平板上に回折
格子部を設けた回折光学素子について示したがレンズ表
面に設けても同様の効果が得られる。In each embodiment, a diffractive optical element having a diffraction grating portion provided on a flat plate has been described. However, the same effect can be obtained by providing the diffractive optical element on the lens surface.
【0041】また、本実施形態では、回折次数が1次光
の場合を示したが、1次光に限定するものではなく、2
次光などの異なった回折光であっても、設計波長を回折
作用を生じる構造の間で変化させることで同様の効果が
得られる。In this embodiment, the case where the diffraction order is the first-order light has been described.
Even for different diffracted lights such as the next light, the same effect can be obtained by changing the design wavelength between structures that cause a diffractive action.
【0042】図8は本発明の回折光学素子を双眼鏡等の
観察光学系に適用したときの実施形態1の要部概略図で
ある。同図は光路を展開した状態を示している。FIG. 8 is a schematic view of a main part of the first embodiment when the diffractive optical element of the present invention is applied to an observation optical system such as binoculars. The figure shows a state where the optical path is expanded.
【0043】図中、83は観察光学系の光軸、87は対
物レンズ、81は回折光学素子であり、図1に示す構成
より成っている。88は像反転プリズムであり、光路を
展開したガラスブロックで示している。対物レンズ87
により被写体(不図示)を回折光学素子81と像反転プ
リズム88を介して1次結像面85に結像している。そ
して接眼レンズ89を介し1次結像面85に形成した正
立像をアイポイント86より観察している。回折光学素
子81は対物レンズ87により発生する1次結像面85
における色収差等を補正している。In the drawing, reference numeral 83 denotes an optical axis of the observation optical system, 87 denotes an objective lens, and 81 denotes a diffractive optical element, which is configured as shown in FIG. Reference numeral 88 denotes an image reversing prism, which is indicated by a glass block having an expanded optical path. Objective lens 87
Thus, a subject (not shown) is imaged on the primary image plane 85 via the diffractive optical element 81 and the image inverting prism 88. Then, the erect image formed on the primary image forming surface 85 via the eyepiece lens 89 is observed from the eye point 86. The diffractive optical element 81 has a primary image plane 85 generated by the objective lens 87.
Are corrected.
【0044】本実施形態では、対物レンズ1の近傍に回
折光学素子1を形成した場合を示したが、これに限定す
るものではなく、像反転プリズム8の表面や接眼レンズ
9内の位置であっても同様の効果が得られる。In the present embodiment, the case where the diffractive optical element 1 is formed in the vicinity of the objective lens 1 has been described. However, the present invention is not limited to this, and the position may be the surface of the image inverting prism 8 or the position in the eyepiece lens 9. The same effect can be obtained.
【0045】回折光学素子1を1次結像面5より物体側
に設けることで対物レンズ7のみでの色収差の低減効果
があるため、肉眼の観察系の場合少なくとも対物レンズ
側に設けることが望ましい。By providing the diffractive optical element 1 on the object side with respect to the primary image forming plane 5, there is an effect of reducing chromatic aberration only by the objective lens 7, and therefore, it is desirable to provide the diffractive optical element 1 on at least the objective lens side in the case of a naked eye observation system. .
【0046】また、本実施形態では、双眼鏡の場合を示
したが、これに限定するものではなく、地上望遠鏡や天
体観測用望遠鏡等での光学機器であってもよく、またレ
ンズシャッターカメラやビデオカメラ等の光学式のファ
インダーであっても同様の効果が得られる。In this embodiment, the case of binoculars has been described. However, the present invention is not limited to this, and optical equipment such as a terrestrial telescope or a telescope for astronomical observation may be used. The same effect can be obtained even with an optical finder such as a camera.
【0047】[0047]
【発明の効果】本発明によれば以上のように、回折効果
を利用して色収差補正等の所定の光学性能を得る際に基
板上を複数の領域に分割し、各領域毎に格子段数及び格
子厚の異なる互いに異なるレンズ作用を有する所定形状
の回折格子を形成した格子部を設定することによって設
計次数の回折効率を使用波長領域全域で高く、良好なる
光学性能が容易に得られる回折光学素子及びそれを用い
た光学系を達成することができる。According to the present invention, as described above, when obtaining predetermined optical performance such as chromatic aberration correction using the diffraction effect, the substrate is divided into a plurality of regions, and the number of grating stages and A diffractive optical element capable of easily obtaining good optical performance by setting a grating portion having a diffraction grating of a predetermined shape having different lens functions with different grating thicknesses, thereby increasing the diffraction efficiency of the design order over the entire use wavelength range. And an optical system using the same.
【図1】 本発明の実施形態1の要部平面図FIG. 1 is a plan view of a main part of a first embodiment of the present invention.
【図2】 図1の一部分の拡大断面図FIG. 2 is an enlarged sectional view of a part of FIG.
【図3】 本発明の実施形態1の回折光学素子の成形型
の製造手段の説明図FIG. 3 is an explanatory view of means for manufacturing a mold for a diffractive optical element according to the first embodiment of the present invention.
【図4】 本発明の実施形態2の回折光学素子の成形型
の製造手段の説明図FIG. 4 is an explanatory view of means for manufacturing a mold for a diffractive optical element according to a second embodiment of the present invention.
【図5】 本発明の実施形態3の回折光学素子の回折効
率特性の説明図FIG. 5 is an explanatory diagram of a diffraction efficiency characteristic of the diffractive optical element according to the third embodiment of the present invention.
【図6】 従来の回折光学素子の格子断面の説明図FIG. 6 is an explanatory view of a grating cross section of a conventional diffractive optical element.
【図7】 従来の回折光学素子の成形型の製造手順の説
明図FIG. 7 is an explanatory diagram of a manufacturing procedure of a conventional mold for a diffractive optical element.
【図8】 本発明の回折光学素子を用いた光学系の実施
形態1の要部概略図FIG. 8 is a schematic diagram of a main part of an optical system using the diffractive optical element according to the first embodiment of the invention.
1 回折光学素子 2 第1格子部 3 第2格子部 4 第3格子部 81 回折光学素子 83 光軸 85 1次結像面 86 評価面(アイポイント) 87 対物レンズ 88 プリズム 89 接眼レンズ DESCRIPTION OF SYMBOLS 1 Diffractive optical element 2 1st grating part 3 2nd grating part 4 3rd grating part 81 Diffractive optical element 83 Optical axis 85 Primary imaging surface 86 Evaluation surface (eye point) 87 Objective lens 88 Prism 89 Eyepiece
Claims (8)
とに格子段数及び格子厚が異なるレンズ作用を有する断
面形状が階段形状より成る回折格子を設けて複数の格子
部を形成しており、該複数の格子部は回折効率の高くな
る波長が互いに異なっていることを特徴とする回折光学
素子。1. A substrate is divided into a plurality of regions, and a plurality of grating portions are formed by providing a diffraction grating having a stepped cross-sectional shape having a lens action in which the number of grating steps and the grating thickness are different for each region. A diffractive optical element, wherein the plurality of grating portions have different wavelengths at which diffraction efficiency is increased.
されるとき、該格子部は特定次数に光束が集光している
ことを特徴とする請求項1の回折光学素子。2. The diffractive optical element according to claim 1, wherein when light of a predetermined wavelength is diffracted by the plurality of grating portions, the grating portions converge a light beam to a specific order.
数の大きい格子部が、設計波長が長波長であることを特
徴とする請求項1記載の回折光学素子。3. The diffractive optical element according to claim 1, wherein a design wavelength of the diffractive optical element is such that a grating portion having a large number of grating steps has a longer design wavelength.
子部内、最も少ない格子段数からなる格子部の各格子厚
形状と、他の格子部の前記最小段数までの各格子厚形状
が等しいことを特徴とする請求項1記載の回折光学素
子。4. A diffraction grating according to claim 1, wherein each of the grating portions having the smallest number of grating stages in the grating portions having different grating stages has the same thickness as each of the other grating portions up to the minimum stage number. The diffractive optical element according to claim 1, wherein:
アル方向に同心円状に分割しており、円中心から離れる
に従った格子部の方が格子厚が減少していることを特徴
とする請求項1記載の回折光学素子。5. A plurality of grating portions of the diffractive optical element are divided concentrically in the radial direction, and the grating thickness decreases as the grating portion moves away from the center of the circle. The diffractive optical element according to claim 1.
折光学素子をその格子部の異なる格子段数の内、最も大
きい格子段数(最大段数)をm1、nを整数としたとき 2n <m1≦2n+1 を満足する(n+1)個のマスクを用いて製造している
ことを特徴とする回折光学素子の製造方法。6. Among the different lattice stages the diffractive optical element of the lattice portion of any one of claims 1 5, 2 n when the largest lattice stages (maximum number) was m1, n is an integer A method for manufacturing a diffractive optical element, wherein the manufacturing is performed using (n + 1) masks satisfying <m1 ≦ 2n + 1 .
折光学素子を用いたことを特徴とする光学系。7. An optical system using the diffractive optical element according to claim 1. Description:
造した回折光学素子を用いていることを特徴とする光学
系。8. An optical system using the diffractive optical element manufactured by the method for manufacturing a diffractive optical element according to claim 6.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP34218697A JPH11160512A (en) | 1997-11-27 | 1997-11-27 | Diffraction optical element and optical system using the same |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP34218697A JPH11160512A (en) | 1997-11-27 | 1997-11-27 | Diffraction optical element and optical system using the same |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH11160512A true JPH11160512A (en) | 1999-06-18 |
Family
ID=18351787
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP34218697A Pending JPH11160512A (en) | 1997-11-27 | 1997-11-27 | Diffraction optical element and optical system using the same |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH11160512A (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2010085625A (en) * | 2008-09-30 | 2010-04-15 | Dainippon Printing Co Ltd | Method for manufacturing three-dimensional patterned body |
US9927616B2 (en) | 2013-01-02 | 2018-03-27 | Massachusetts Institute Of Technology | Methods and apparatus for transparent display using scattering nanoparticles |
CN108121139A (en) * | 2016-11-28 | 2018-06-05 | 精工爱普生株式会社 | Wavelength changing element, light supply apparatus and projecting apparatus |
-
1997
- 1997-11-27 JP JP34218697A patent/JPH11160512A/en active Pending
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2010085625A (en) * | 2008-09-30 | 2010-04-15 | Dainippon Printing Co Ltd | Method for manufacturing three-dimensional patterned body |
US9927616B2 (en) | 2013-01-02 | 2018-03-27 | Massachusetts Institute Of Technology | Methods and apparatus for transparent display using scattering nanoparticles |
CN108121139A (en) * | 2016-11-28 | 2018-06-05 | 精工爱普生株式会社 | Wavelength changing element, light supply apparatus and projecting apparatus |
CN108121139B (en) * | 2016-11-28 | 2021-05-14 | 精工爱普生株式会社 | Wavelength conversion element, light source device, and projector |
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